Materials containing copper (Cu), zinc (Zn), tin (Sn), and at least one of sulfur (S) and selenium (Se) such as Cu2ZnSn(S,Se)4 (CZT(S,Se)) are earth-abundant and can be used as light absorbing materials in solar cells. In fact, solar cells made with CZT(S,Se) as the light absorbing layer are very attractive due to the material's stability and low toxicity. However, CZTSSe suffers from large voltage deficits (band gap—open circuit voltage Voc) that can affect device performance.
Thus, CZT(S,Se)-based solar cells and techniques for formation thereof that produce improved device performance and yield would be desirable.